The work proposed here will provide a description of the neural mechanisms underlying two of the visual systems most important functions: 1) the ability of the retina to operate over extended ranges of lighting conditions, and 2) the ability of the retina to signal change versus relative permanence in the visual environment. Glutamate receptors at excitatory synapses in bipolar cells and amacrine cells are key to our understanding these processes, and l shall study these membrane proteins by means of a combination of newly developed and powerful techniques; including patch clamp recordings of single identified neurons in the retinal slice preparation, as well as in an isolated preparation. We are exploring the possibility that glutamate receptors exists in bipolar cells in a number of subtypes, and that these subtypes confer on the neurons specific functional properties. For example, some glutamate receptors in bipolar cells may carry the signal from the rod photoreceptors while others carry the cone signal. Further, the rod and cone signals at the glutamate receptors in bipolar cells can be modified through a neurochemical (dopamine) mechanisms in the retina that may help to adjust the strength of the rod and cone signals under different lighting conditions. And in amacrine cells, some glutamate receptors mediate a rapid response in the transient amacrine cells, which signals a change in the environment, while other glutamate receptors mediate long responses, serving to signal the relative permanence of information. By providing a detailed biophysical and biochemical description of the excitatory pathways in bipolar and amacrine cells, a clearer understanding of the mechanisms important for visual function at the retinal level will be advanced. Thus an understanding of retinal function and dysfunction at the biochemical level is advanced with the possibility of then developing pharmacological therapies for those now biochemically defined dysfunctions.